For example, a double cavity type toroidal continuously variable transmission which is used as a vehicle transmission is configured as illustrated in FIGS. 6 and 7. As illustrated in FIG. 6, an input shaft 1 is rotatably supported on an inner side of a casing 50, and two input side disks 2, 2, and two output side disks 3, 3 are provided to an outer circumference of the input shaft 1. An output gear 4 is rotatably supported on the outer circumference of a middle portion of the input shaft 1. The output side disks 3, 3 are connected to cylindrical flange portions 4a, 4a provided in the center portion of the output gear 4 by spline-coupling.
The input shaft 1 is driven to rotate by a driving shaft 22 via a loading cam type pressing device 12 which is provided between the input side disk 2 and a cam plate (loading cam) 7 which are positioned on the left side in the drawing. The output gear 4 is supported in the casing 50 via a partition wall 13 which is configured by connecting two members, and accordingly, the output gear 4 is prohibited from displacement in an axis O direction while being rotatable around an axis O of the input shaft 1.
The output side disks 3, 3 are rotatably supported around the axis O of the input shaft 1 by needle bearings 5, 5 which are interposed between the output side disks 3, 3 and the input shaft 1. The input side disk 2 on the left side in the drawing is supported by the input shaft 1 via a ball spline 6, the input side disk 2 on the right side in the drawing is spline-coupled to the input shaft 1, and the input side disks 2 rotate together with the input shaft 1. A power roller 11 (refer to FIG. 7) is interposed to be rotatable between inner surfaces (recessed surface: also referred to as a traction surface) 2a, 2a of the input side disks 2, 2, and inner surfaces (recessed surface: also referred to as a traction surface) 3a, 3a of the output side disks 3, 3.
On an inner circumferential surface 2c of the input side disk 2 which is positioned on the right side in FIG. 6, a step portion 2b is provided. A step portion 1b provided on an outer circumferential surface 1a of the input shaft 1 abuts against the step portion 2b, and a back face (right surface of FIG. 6) of the input side disk 2 abuts against a loading nut 9 screwed to a screw portion formed on the outer circumferential surface of the input shaft 1. Accordingly, displacement in the axis O direction with respect to the input shaft 1 of the input side disk 2 is substantially prohibited. A leaf spring 8 is provided between the cam plate 7 and a flange portion 1d of the input shaft 1. The leaf spring 8 applies a pressing force (preload) to an abutting portion between the recessed surfaces 2a, 2a, 3a, 3a of each of disks 2, 2, 3, 3, and circumferential surfaces 11a, 11a of the power rollers 11, 11.
FIG. 7 is a sectional view along line A-A of FIG. 6. As illustrated in FIG. 7, the inner side of the casing 50 is provided with one pair of trunnions 15, 15 which swing around one pair of pivots 14, 14 which are provided at a skew position with respect to the input shaft 1. In FIG. 7, the input shaft 1 is omitted in the drawing. Each trunnion 15, 15 has one pair of bent wall portions 20, 20 which are formed while being bent on the inner surface side of a support plate portion 16 at both end portions of the support plate portion 16 in the longitudinal direction (upper-lower direction of FIG. 7). By the bent wall portions 20, 20, a recessed pocket portion P for accommodating the power roller 11 therein is formed in each trunnion 15, 15. Each pivot 14, 14 is provided concentrically on the outer surface of each bent wall portion 20, 20.
A circular hole 21 is formed in the center portion of the support plate portion 16, and a base end portion (first shaft portion) 23a of a displacement shaft 23 is supported by the circular hole 21. By swinging each trunnion 15, 15 around each pivot 14, 14, an inclination angle of the displacement shaft 23 supported by the center portion of each trunnion 15, 15 is adjusted. In the surrounding of a tip end portion (second shaft portion) 23b of the displacement shaft 23 which protrudes from the inner surface of each trunnion 15, 15, each power roller 11 is rotatably supported, and each power roller 11, 11 is interposed between each input side disk 2, 2 and each output side disk 3, 3. The base end portion 23a and the tip end portion 23b of each displacement shaft 23, 23 are displaced to each other.
The pivots 14, 14 of each trunnion 15, 15 are supported to be swingable with respect to one pair of yokes 23A, 23B and to be displaceable in the axial direction (upper-lower direction of FIG. 7), and movement of the trunnions 15, 15 in the horizontal direction is regulated by each yoke 23A, 23B. Each yoke 23A, 23B is formed in a rectangular shape by press machining or forge processing of a metal, such as steel. Four circular support holes 18 are provided at four corners of each yoke 23A, 23B, and each pivot 14 provided in both end portions of the trunnion 15 is supported to be swingable via radial needle bearings 30 in the support holes 18. In the center portion of the yokes 23A, 23B in the width direction (left-right direction of FIG. 6), a circular locking hole 19 is provided, and the inner circumferential surface of the locking holes 19 is internally fitted with spherical surface posts 64, 68 as cylindrical surfaces. In other words, the yoke 23A on the upper side is supported to be swingable by the spherical surface post 64 which is supported by the casing 50 via a fixing member 52, and the yoke 23B on the lower side is supported to be swingable by the spherical surface post 68 and an upper cylinder body 61 of a driving cylinder 31 supported by the spherical surface post 68.
In addition, each displacement shaft 23, 23 provided in each trunnion 15, 15 is provided at positions opposite to each other at 180 degrees with respect to the input shaft 1. The direction in which the tip end portion 23b of each displacement shaft 23, 23 are displaced to the base end portion 23a is the same direction (upper-lower reverse direction in FIG. 7) in the rotational direction of the disks 2, 2 and the disks 3, 3. The displacement direction is the direction which is substantially orthogonal to the installation direction of the input shaft 1. Therefore, each power roller 11, 11 is supported to be slightly displaceable in the longitudinal direction of the input shaft 1. As a result, even in a case where each power roller 11, 11 tends to be displaced in the axial direction of the input shaft 1 due to elastic deformation or the like of each constituent member based on a thrust load generated by the pressing device 12, the displacement is absorbed without applying an excessive force to each constituent member.
Further, between the outer surface of the power roller 11 and the inner surface of the support plate portion 16 of the trunnion 15, a thrust ball bearing (thrust bearing) 24 which is a thrust rolling bearing and a needle roller thrust bearing 25 are provided in an order from the outer surface of the power roller 11. The thrust ball bearing 24 allows each power roller 11 to rotate while supporting the load in the thrust direction applied to each power roller 11. The thrust ball bearing 24 includes a plurality of balls (hereinafter, referred to as a rolling element) 26, 26, a circular cage 27 which rollably holds each ball 26, 26, and a circular outer ring 28. An inner ring raceway of each thrust ball bearing 24 is formed on the outer surface (large end face) of each power roller 11, and an outer ring raceway is formed on the inner surface of each outer ring 28.
The needle roller thrust bearing 25 is interposed between the inner surface of the support plate portion 16 of the trunnion 15 and the outer surface of the outer ring 28. The needle roller thrust bearing 25 allows the power roller 11 and the outer ring 28 to swing around the base end portion 23a of each displacement shaft 23 while supporting the thrust load applied to each outer ring 28 from the power roller 11.
Further, a driving rod (trunnion shaft) 29 is provided in one end portion (lower end portion of FIG. 7) of each trunnion 15, 15, and a driving piston (hydraulic piston) 33 are fixed to the outer circumferential surface of the intermediate portion of each driving rod 29, 29. Each driving piston 33, 33 is oil-tightly fitted into the driving cylinder 31 configured by the upper cylinder body 61 and a lower cylinder body 62. A driving device 32 which displaces each trunnion 15, 15 in the axial direction of the pivots 14, 14 of the trunnions 15, 15 is configured by each driving piston 33, 33 and the driving cylinder 31.
In a case of the toroidal continuously variable transmission configured in this manner, the rotation of the input shaft 1 is transmitted to each input side disk 2, 2 via the pressing device 12. The rotation of the input side disks 2, 2 is transmitted to each output side disk 3, 3 via the pair of power rollers 11, 11, and further, the rotation of each output side disk 3, 3 is taken out of the output gear 4.
When a rotational speed ratio between the input shaft 1 and the output gear 4 is changed, the pair of driving pistons 33, 33 are displaced in directions reverse to each other. According to the displacement of each driving piston 33, 33, the pair of trunnions 15, 15 are displaced in the directions reverse to each other. For example, the power roller 11 on the left side in FIG. 7 is displaced to the lower side in FIG. 7, and the power roller 11 on the right side in FIG. 7 is displaced to the upper side in FIG. 7.
As a result, the orientation of a force in the tangential direction which acts on the abutting portion between the circumferential surfaces 11a, 11a of each power roller 11, 11, and inner surfaces 2a, 2a, 3a, 3a of each input side disk 2, 2 and each output side disks 3, 3 changes. According to the change in the orientation of the force, each trunnion 15, 15 swings (tilts) in directions reverse to each other around the pivots 14, 14 supported by the yokes 23A, 23B.
As a result, an abutting position between the circumferential surfaces 11a, 11a of each power roller 11, 11 and each inner surface 2a, 3a changes, and the rotational speed ratio between the input shaft 1 and the output gear 4 changes. When torque to be transmitted varies between the input shaft 1 and the output gear 4 and an elastic deformation amount of each constituent member changes, each power roller 11, 11 and the outer rings 28, 28 attached to each power roller 11, 11, slightly rotate around the base end portions 23a, 23a of each displacement shaft 23, 23. Since each needle roller thrust bearing 25, 25 is provided between the outer surface of each outer ring 28, 28 and the inner surface of the support plate portion 16 which configures each trunnion 15, 15, the rotation is smoothly performed. Therefore, as described above, the force for changing the inclination angle of each displacement shaft 23, 23 can be small.
Incidentally, in a double cavity type toroidal continuously variable transmission, as illustrated in FIGS. 8 and 9, an integrated type output side disk 34 is used where a pair of output side disks 3, 3 are integrated with each other while rear surfaces of the pair of output side disks 3, 3 disposed between the pair of input side disks 2, 2 are connected to each other, and the outer circumferential surface of such integrated output side disks 3, 3 is formed with teeth 41 to serve as the output gear 4 (for example, refer to Patent Document 1 and Patent Document 2).
In manufacturing the integrated type output side disk 34, after performing heat treatment together with cutting the gear (processing the gear teeth) on the outer circumferential portion and before performing traction surface processing on the inner surfaces 3a, 3a of the integrated type output side disk 34, a reference plane 43 is formed on the outer circumferential portion of the integrated type output side disk 34 for the traction surface processing and inner diameter grinding of a through hole 34a of the integrated type output side disk 34. The width of the formed reference plane 43 in the axial direction of the integrated type output side disk 34 is same as the width of the teeth 41 formed on the integrated type output side disk 34 in the axial direction of the integrated type output side disk 34. The width of the teeth 41 is same as the width (the thickness in the axial direction of the outer circumferential portion of the integrated type output side disk 34) of the outer circumferential portion of the integrated type output side disk 34.
In FIGS. 8 and 9, the output gear portion of the integrated type output side disk 34 is briefly illustrated, and the output gear portion may be, for example, a helical gear. Four circles illustrating the gear in FIG. 8 are a teeth tip circle, a reference circle, a base circle, and a teeth bottom circle in an order from the outer side, and the reference plane 43 is formed at a portion of the teeth tip circle.